From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E584C433DF for ; Mon, 24 Aug 2020 08:50:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F12ED204FD for ; Mon, 24 Aug 2020 08:50:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259029; bh=E9RoHVS97+ZIu745TjSEl0N6lC02FWnHn7mS2W69IC4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=we4DDy13Eg7ZptOyfYyef3gMXEBee8vG+8cgI71gWBNObGjEOIQBQReHgMblAzYrr ati7F0JDucv3tJknYrgCGpktNsGh2hxWgs/7ZjNGbenXaHkGPwCKql7y8S04ejl7hj sr2k/CBRMJcI6XGHyrozuqn8yqZhyhF9FNTEbSM4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729119AbgHXIuY (ORCPT ); Mon, 24 Aug 2020 04:50:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:53706 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729805AbgHXIuR (ORCPT ); Mon, 24 Aug 2020 04:50:17 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A399D204FD; Mon, 24 Aug 2020 08:50:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598259017; bh=E9RoHVS97+ZIu745TjSEl0N6lC02FWnHn7mS2W69IC4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sM63lY00xXs1wf2yGEJGxIP6P6pHQBaCXYkjksv3wiZ47FCEmZDlD5TsilFEd4w4+ iknAUT2DUK+gUepGRLbAqe9sn0CrmYFGAQQMRSDMq50mW1I8ms4XFqwHt+CTPCPekM FgUaSQe0xPn67wK6FbL6hCKzpqVPwY/ODDJwT49g= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mao Wenan , "Michael S. Tsirkin" , Jason Wang , Sasha Levin Subject: [PATCH 4.4 23/33] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Date: Mon, 24 Aug 2020 10:31:19 +0200 Message-Id: <20200824082347.692579325@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200824082346.498653578@linuxfoundation.org> References: <20200824082346.498653578@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mao Wenan [ Upstream commit 481a0d7422db26fb63e2d64f0652667a5c6d0f3e ] The loop may exist if vq->broken is true, virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split will return NULL, so virtnet_poll will reschedule napi to receive packet, it will lead cpu usage(si) to 100%. call trace as below: virtnet_poll virtnet_receive virtqueue_get_buf_ctx virtqueue_get_buf_ctx_packed virtqueue_get_buf_ctx_split virtqueue_napi_complete virtqueue_poll //return true virtqueue_napi_schedule //it will reschedule napi to fix this, return false if vq is broken in virtqueue_poll. Signed-off-by: Mao Wenan Acked-by: Michael S. Tsirkin Link: https://lore.kernel.org/r/1596354249-96204-1-git-send-email-wenan.mao@linux.alibaba.com Signed-off-by: Michael S. Tsirkin Acked-by: Jason Wang Signed-off-by: Sasha Levin --- drivers/virtio/virtio_ring.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index a01a41a412693..6b3565feddb21 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -603,6 +603,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx) { struct vring_virtqueue *vq = to_vvq(_vq); + if (unlikely(vq->broken)) + return false; + virtio_mb(vq->weak_barriers); return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx); } -- 2.25.1